Improved detection of house infestations with triatomines using sticky traps: a paired-comparison trial in the Argentine Chaco

Abstract

Background: We conducted a matched-pairs trial of three methods for detecting house infestation with triatominae bugs in a well-defined endemic rural area in the Argentine Chaco. Methods: The three methods included a simple double-sided adhesive tape (ST) installed near host resting sites; timed-manual collections with a dislodging aerosol (TMC, the reference method used by vector control programmes), and householders' bug notifications (HN). Triatomine infestations were evaluated in 103 sites of 54 houses, including domiciles, kitchens and storerooms. Results: In domiciles where Triatoma infestans was collected, sensitivity of each single method decreased from 79% by ST and 77% by HN, to 57% by TMC, and increased to 92% when ST was combined with HN. In peridomestic kitchens and storerooms, TMC was relatively as sensitive as ST and significantly more sensitive than HN. On average, the number of bugs recovered by ST was 0.94 times that collected by TMC. The ST mainly collected early-instar nymphs whereas TMC yielded late (larger) stages. Triatomines caught by ST had significantly lower mean weight-to-length ratios and lower blood-feeding rates than those caught by TMC, suggesting the ST intercepted and trapped vectors seeking a blood meal host. Conclusions: The ST may effectively replace TMC for detecting T. infestans in domiciles, and is especially apt for early detection of low-density domestic infestations in the frame of community-based surveillance or elimination programmes; decision making on whether an area should be targeted for full-coverage insecticide spraying, and to corroborate that extant conditions are compatible with the interruption of vector-borne transmission.

Towards environmental detection of Chagas disease vectors and pathogen

“…Under simulated conditions of degradation, R. prolixus eDNA was shown to be stable on FTA cards for at least two weeks at room temperature, which aligns with previous studies reporting successful pathogen isolation from cards stored for several weeks under similar conditions; published observations indicate longer-term stability can be achieved when FTA cards are stored at 4 o C [39]. In the field specimens, R. prolixus eDNA was detected from infested houses with an estimated sensitivity of 60.6% which is comparable with reported detection levels for TMCs, householder collections and other trapping techniques [25,28,57]. Given that household triatomine presence was self-reported, one explanation for the number of false negative houses may be inaccuracies in resident reports, infestation with other local triatomine species (ten triatomine species, including R. prolixus, Triatoma maculata and Panstrongylus geniculatus, have been identified in Casanare [58]), relative sensitivity of using cotton-tipped swabs (these are not specifically optimised for DNA capture like FTA cards), or the LOD of our qPCR assay.…”

“…Community-based bug collections or bug notifications (with or without proof of collection) performed by householders have reported similar or sometimes superior levels of sensitivity to TMCs [25][26][27], but are prone to variability due to changes in motivation and skills of local voluntary residents [22,25]. Additional passive devices, including double-sided sticky traps and artificial shelter units, often supplemented with semiochemical attractants, have shown more promising results in some endemic communities [28][29][30]. Following triatomine bug collection, further incrimination of risk of T. cruzi infection requires triatomine hindgut dissection and microscopic parasite visualization, parasite isolation by haemoculturing, or direct DNA extraction from faeces and PCR-based detection methods [31].…”

Control of pyrethroid‐resistant populations of Triatoma infestans, the main vector of Trypanosoma cruzi, by treating dogs with fluralaner in the Argentine Chaco

“…This and the relative imprecision of householder reports on dog exposure may explain the lack of effect of the latter variable in the extended regression models. Triatoma infestans blood‐fed every 4–7 to 10 days in the Argentine Chaco mid‐spring (e.g., Enriquez et al, 2020; Gürtler et al, 2014) and rarely did it over late fall and winter (Ceballos et al, 2005), when fluralaner would not exert any effect on triatomines.…”

Improved vector control of Triatoma infestans limited by emerging pyrethroid resistance across an urban-to-rural gradient in the Argentine Chaco

“…Community-based triatomine surveillance was meant to provide additional evidence, and has worked effectively in Avia Terai and elsewhere [ 11 , 34 , 51 , 57 ]. Timed-manual searches and householder notifications revealed 70% and 54% of actual house-level infestations detected by a range of methods, respectively [ 58 ]. Their combined outcome would roughly reveal 80% of all house infestations detected, more so in domestic habitats (87%); thus, the observed prevalence of infestation adjusted for imperfect detection would increase relatively by 15–25% and would hardly affect the qualitative conclusions in this paper.…”